Lets talk DIY turbos & DynoJet tuning

[CarterKraft]

Wifes rig has the 800cc Rotax V-twin.
Because I am a tight ass I didn't want to spring for the extra 200cc at the tune of close to $5k at the time of purchase.

At home and sub 1000' of elevation its fine, even plenty of power really even though it is only rated at 50 hp.
I think ideal is a 100 hp at elevation. While that is doubling the engines HP I don't think it is as extreme as it sounds as this engine in other configurations (1000R for example) makes 125hp NA. The machine at 50" wide is underpowered on purpose to fit into the 50" trail class.
The same machine in the "60" Sport 1000" configuration makes 75hp. That would be a fine target as well.

At elevation 10'k + it starts weazing as you can imagine.
I have thought all along I would just turbo it.
Now seems to be the time, we are planning on a adults only CO trip next year where we will both be riding in it on some long trips, more power at altitude will be welcome.
Force Turbo makes a kit, they don't specify for 800/1000 but I'd assume its for the 1k.
I have not talked to them but the only turbo they advertise to sell on their site is a Garrett GT2860RS, it has a 76 trim compressor and a .86 A/R turbine housing.

Playing with some calculators I was coming up with a pressure ratio of 1.5 for a 800cc pump gas engine making 100 hp on 5 ish psi boost.
That was also around 9-11 lbs/min of fuel.
Looking at these maps it seems like this turbo is way too big for this engine and power level. At minimum the A/R is wrong and needs to be brought down.

Anyone have any input as to turbo sizing for these small displacement engines?
The GT25 is the smallest "racing" ball bearing turbo they make but they have the "club line" turbos that go much smaller in size, but with journal bearings.
The 14 seemed to be in the range but the 17 is possibly a better fit for lower boost higher flow.

 

[CarterKraft]

The GBC 17-250 map looks much better, albeit still under the meat of the map at this theoretical flow.

The 14-200 is not much different so it's possible my math is off and the pressure ratio or lbs/min are much higher than my calculations.

 

[TrailTamer]

it is only rated at 50 hp.
I think ideal is a 100 hp at elevation. While that is doubling the engines HP I don't think it is as extreme as it sounds as this engine in other configurations (1000R for example) makes 125hp NA. The machine at 50" wide is underpowered on purpose to fit into the 50" trail class.
The same machine in the "60" Sport 1000" configuration makes 75hp. That would be a fine target as well.

In that case will it be easier and more reliable to swap a crate engine intended for a “60” Sport 1000” or 1000R in it?

What derated your wifey’s toy to 50hp if it’s the same engine from 75hp to over double power at 125hp N/A?

 

[CarterKraft]

In that case will it be easier and more reliable to swap a crate engine intended for a “60” Sport 1000” or 1000R in it?

What derated your wifey’s toy to 50hp if it’s the same engine from 75hp to over double power at 125hp N/A?

Back when I looked into converting the 50-75-125 there was things like exhaust, cams, pistons (compression) and throttle bodies/intakes.
Normal stuff IMO for tuning UP a engine.

Forced induction should negate any of the need for those components (alone) to get a modest increase in HP.
If 100 HP is out of line then 75 would be fine.
As far as I have found a engine swap is not worth it $$$ wise, unless I lucked on to a complete wrecked machine of the correct power.
I should be able to turbo kit for under $2k and have much better torque rise and power band.

 

[CarterKraft]

In that case will it be easier and more reliable to swap a crate engine intended for a “60” Sport 1000” or 1000R in it?

What derated your wifey’s toy to 50hp if it’s the same engine from 75hp to over double power at 125hp N/A?

And you have been warned, I am a little like some of the hard asses on this board, I want to do what I want to do.
It might be dumb but I WANT to build a turbo kit.

The sizing is what I am stumbling on, follow the pack or do the best of what I think is right?

 

[CarterKraft]

Response from Force Turbo on the subject:

"
Hello Weldon,

Our turbo system would need to have some adjustment done to it. Here they are.

Fitment of Parts= You may need to weld and change some angles or the way the product fits in the machine. If you would like, We could just sell raw parts as well.

Turbo = I would recommend going with a smaller AR on the turbo Exhaust housing to compensate for the smaller displacement engine.

Fuel controller = would work.

Other than that it is all the same.

Let me know if you have any other questions or you want to get a turbo system assembled for your application.

Thanks, Bryce



On Thu, Jul 13, 2023 at 1:53 PM Weldon Carter <> wrote:

Do you guys have any input as to how your turbo system would work on a ’18 800 Maverick Trail at 10-12k’ elevation?

Do you have a smaller turbo option to compensate for the smaller displacement of the 800?

 

[CarterKraft]

I keep fucking around with the Garret boost advisor and I still come up with the same thing, that 2860 is waaayyy too big...

Which confused the shit out of me.
Is this sizing deal because it's running a CVT? They suggested keeping stock clutching which I wouldn't have guessed.

Am I fucking up the math by inputing 10k elevation and 75* F ambient temps?

 

[SLOWPOKE693]

IMO you size the turbo according to its use. If you want bottom end power you go with a small quick spooling turbo. If you want big HP at high RPM you go with a big turbo that takes time and RPM to spool up.

 

[CarterKraft]

Heres an example.
.8L
desired crank shaft hp 85
2500' elevation
85 ambient temp
4 valve per cyl
1 turbo
no intercooler

 

[CarterKraft]

IMO you size the turbo according to its use. If you want bottom end power you go with a small quick spooling turbo. If you want big HP at high RPM you go with a big turbo that takes time and RPM to spool up.

I was hoping you would wander in here...
So with a CVT its sort of all mid range to upper end power?

The 2860 is physically almost double the size of the suggested turbo, I am doing something wrong I think.

 

[CarterKraft]

another example
.8L
desired crank shaft hp 65
10k' elevation
75 ambient temp
4 valve per cyl
1 turbo
no intercooler
8500 rpm peak hp

 

[TrailTamer]

why the boost psi is so low, almost like if its N/A?

 

[SLOWPOKE693]

So with a CVT its sort of all mid range to upper end power?

That's the way I interpret it. The engine never sees low rpm with a CVT so there really isn't a need to have it spooling and building boost at such a low rpm, hence why the bigger turbo fits in this application.

 

[CarterKraft]

why the boost psi is so low, almost like if its N/A?

Fuck if I know.
I'm gonna download the app and see if I get something different.

 

[CarterKraft]

That's the way I interpret it. The engine never sees low rpm with a CVT so there really isn't a need to have it spooling and building boost at such a low rpm, hence why the bigger turbo fits in this application.

The turbo force is using is a 350 hp capacity charger, I can't see the reason to need something that big for a 75-95hp target

 

[SLOWPOKE693]

The turbo force is using is a 350 hp capacity charger, I can't see the reason to need something that big for a 75-95hp target

Who said you dont need 350hp?

 

[CarterKraft]

Who said you dont need 350hp?

I mean I don't... I don't need what all comes with that, belts trans, axles etc.
If I could realistically keep the 50hp at sea level up to 11k' it would be awesome.


Here's a 200hp X3 turbo upgrade.

"• OE X3 RR (20-up) compressor wheel measures 35.8mm, Pure CNC milled wheel is 42mm with an additional 6 full and 6 splitter blade configuration.
.• OE X3 RR turbine wheel is 35mm, Pure wheel is 42mm with blade geometry designed for improved mass flow."

The GBC14-200 (smallest they make)

"Forged, fully-machined compressor wheels with advanced aero is offered in 34mm inducer size and 46mm exducer. GBC14-200 can support from 140-200 350 horsepower. The compressor wheel is a 55 trim and the Compressor housing A/R is 0.52 A/R. This turbocharger can support up to 22 lbs/min of airflow and up to 2.8 pressure ratio."

 

[CarterKraft]

I'm gonna call some turbo shops, not turbo kit shops and see what they say.
I'm realistically looking to gain 25hp at sea level and keep the stock 50 at altitude. 100hp was a fun goal but not really needed if I think about it.

What's the HP peak rpm on the Talon?

 

[SLOWPOKE693]

What's the HP peak rpm on the Talon?

I believe it's right around 7,400rpm.

 

[SLOWPOKE693]

I know you don't want to hear this buy I have to say it......

Are you sure you want to go down this rabbit hole for 25hp? If you don't start with some kind of "kit" you will have to source everything yourself and I'm willing to bet that doing that along with the trial and error factor will have you well past your target budget and probably up to your eyeballs in headaches trying to get it tuned and to run how you want it.

Unless I was trying to double the HP # of a stock N/A machine I wouldn't bother with a turbo setup. Higher compression pistons, a cam and some head work will get you all of 25hp without the bullshit and headaches.

 

[CarterKraft]

I know you don't want to hear this buy I have to say it......

Are you sure you want to go down this rabbit hole for 25hp? If you don't start with some kind of "kit" you will have to source everything yourself and I'm willing to bet that doing that along with the trial and error factor will have you well past your target budget and probably up to your eyeballs in headaches trying to get it tuned and to run how you want it.

Unless I was trying to double the HP # of a stock N/A machine I wouldn't bother with a turbo setup. Higher compression pistons, a cam and some head work will get you all of 25hp without the bullshit and headaches.

I'm fine with that too but won't I still be subject to the altitude derate?

I've been looking and big bore up to 13:1 pistons are available, I don't want to get off pump gas (92 is fine).
The only need for extra HP is at altitude.
I'm guessing it's around 35hp at 10k, pretty normal drop.
Going to a 975 is possible, will that help enough at altitude to matter?

Big Bore Cylinder Kit for 800cc engine – MrRPM

www.mrrpmcycle.com

 

[CarterKraft]

I know you don't want to hear this buy I have to say it......

Are you sure you want to go down this rabbit hole for 25hp? If you don't start with some kind of "kit" you will have to source everything yourself and I'm willing to bet that doing that along with the trial and error factor will have you well past your target budget and probably up to your eyeballs in headaches trying to get it tuned and to run how you want it.

Unless I was trying to double the HP # of a stock N/A machine I wouldn't bother with a turbo setup. Higher compression pistons, a cam and some head work will get you all of 25hp without the bullshit and headaches.

Famous last words but the Force turbo kit is really simple. No intercooler even.
And maybe that's there deal, low boost high flow? This is the shit I like doing, stainless welding, aluminum welding etc. much more than engine work.

 

[SLOWPOKE693]

I'd go with the 975 kit with 12-1 pistons and aftermarket cams. With a tune it should make well over 25hp more than what you have now.

 

[SLOWPOKE693]

Famous last words but the Force turbo kit is really simple. No intercooler even.
And maybe that's there deal, low boost high flow? This is the shit I like doing, stainless welding, aluminum welding etc. much more than engine work.

Looks cool, but for only 5psi of boost/25hp it seems like a lot of work. I'm also lazy, so there is that....


EDIT: Does that kit require bigger injectors, and/or bigger fuel pump? Does it require a return fuel system if it's not already equipped with one? Does that kit come with different sensors or is it using stock ones? Does it come with a tune?

 

[CarterKraft]

Looks cool, but for only 5psi of boost/25hp it seems like a lot of work. I'm also lazy, so there is that....


EDIT: Does that kit require bigger injectors, and/or bigger fuel pump? Does it require a return fuel system if it's not already equipped with one? Does that kit come with different sensors or is it using stock ones? Does it come with a tune?

Stock fuel system, uses the DynoJET PV3 with wideband for tuning, same as with big bore kit I imagine.

 

[SLOWPOKE693]

Stock fuel system, uses the DynoJET PV3 with wideband for tuning, same as with big bore kit I imagine.

Does it have cast or forged pistons stock? Cast N/A pistons do not like boost at all and the skirts will crack in short order. Happens to every single Talon that gets the factory approved Jackson Racing turbo kit.

 

[CarterKraft]

Does it have cast or forged pistons stock? Cast N/A pistons do not like boost at all and the skirts will crack in short order. Happens to every single Talon that gets the factory approved Jackson Racing turbo kit.

I'll try to find out, I don't know at the moment.

edit: looking at the pix of the part online they look cast.

 

[CarterKraft]

I did some research into the sizes of the X3 (900cc) and the Jackson turbo kit mentioned above.
My quest is stock power at altitude not increased power (I was greedy with the 100hp benchmark).

So diving into the Jackson Racing turbo kit I found that is a pretty serious power adder, not surprising if they are having hard part failures.
If this what 8 PSI gets you then I definitely don't need much more than 2 or 3...

• 60% increase in power at 8 psi of boost

 

[CarterKraft]

More useless data to support my weak position...
I found there was (might still be) a V-twin 1000 turbo in 2016, made 135 hp stock.
This is the turbo it had.
TD03L4-10TK3-4.8

That turbo in a different variant is used on half the BMW 3.0L N54 engine.

 

[SLOWPOKE693]

I did some research into the sizes of the X3 (900cc) and the Jackson turbo kit mentioned above.
My quest is stock power at altitude not increased power (I was greedy with the 100hp benchmark).

So diving into the Jackson Racing turbo kit I found that is a pretty serious power adder, not surprising if they are having hard part failures.
If this what 8 PSI gets you then I definitely don't need much more than 2 or 3...

• 60% increase in power at 8 psi of boost

Don't forget that those Jackson Turbo systems are intercooled. Non intercooled boost will make less power due to heat soak.

Kraft Werkz is another one to look at for SxS turbo info. They make a kit for my Talon